Earthmoving machines, for example excavating equipment such as rope shovels, are commonly used to move large amounts of earth, rocks or other work materials. Excavating equipment, including rope shovels and other types of excavating equipment, may be propelled by an undercarriage having a pair of parallel tracks that distribute the weight of the excavating equipment so that the equipment can operate on surfaces having varying hardness and undulations. FIG. 1 illustrates one example of an excavating machine in the form of a rope shovel 10 having a body 12 rotatably mounted on an undercarriage 14 for rotation about an axis 16 to position an implement 18 of the machine 10. The implement 18 may be suspended from a boom 20 and maneuvered by a series of cables 22 to operate on work material (not shown). The undercarriage 14 supports the machine 10 on ground 24, and includes a pair of parallel tracks 26 formed from a series of interconnected links 28. The undercarriage 14 includes a series of idler rollers 30 supported at the bottom of a frame assembly 32 and a series of carrier rollers or carrier slides 34 supported at the top of the frame assembly 32 over which the tracks 26 pass to move the machine 10 over the ground 24. A first tumbler 36 is mounted to the frame assembly 32 proximate to the ground 24 at a front end 38 of the undercarriage 14. A drive tumbler 40 is mounted to the frame assembly 32 above the ground 24 at a rear end 42 of the undercarriage 14. The drive tumbler 40 is operatively connected to a power transmission assembly (not shown) of the machine 10, and engages and drives the tracks 26 to move the machine 10 forward and backward as necessary to perform operations on the work material.
FIG. 2 shows one example of the link 28 as known in the art. The link 28 includes a body 44 having a ground engaging surface 46 and an oppositely disposed roller path 48 defined by a pair of lugs 50 extending upwardly from the body 44. The link 28 further includes a pair of male connection portions 52 extending from one side of the body 44, and a pair of female connection portions 54 extending from the opposite side of the body 44 and configured to receive the male portions 52 of the adjacent link 28. After the portions 52, 54 are mated, a pivot pin (not shown) is inserted through openings of the portions 52, 54 to connect the links 28 and allow the links 28 to pivot relative to each other. Returning to FIG. 1, the drive tumbler 40 includes teeth 56 that engage the lugs 50 of the links 28 to drive the tracks 26 forward and in reverse. The teeth 56 of the drive tumbler 40 may be spaced so that the roller path 48 passes over a central portion of the drive tumbler 40, and the roller path 40 and also passes over the idler rollers 30 as the track 26 was passed the idler rollers 30.
When the drive tumbler 40 drives the tracks 26 forward so that the front end 38 is leading the undercarriage 14 across the ground 24, the positioning of the front tumbler 36 proximate to the ground ensures that the tracks 26 roll over the front tumbler 36 and onto the idler rollers 30 without the links 28 buckling between the front tumbler 36 and front idler roller 30. In contrast, when the drive tumbler 40 drives the tracks 26 in reverse and the rear end 42 is leading, a gap between the drive tumbler 40 and the rear idler roller 30R is exposed for engagement by the material forming the ground 24. Ground material engaging the tracks 26 at the gap between the drive tumbler 40 and the rear idler roller 30R can cause the tracks 26 to buckle and drive the links 28 into the frame assembly 32 of the undercarriage 14. The buckling may occur with particular frequency when the machine 10 travels over soft or uneven ground.
FIG. 3 illustrates one example of an undercarriage frame assembly 32 for a crawler crane where buckling of the tracks 26 may occur. The undercarriage frame assembly 32 includes a main frame 58 carrying the idler rollers 30 and the idler tumbler 36, and a unitary end casting 60 mounted at a rear end of the main frame 58 and carrying the drive tumbler 40 and rear idler roller 30R. When the tracks 26 buckle between the drive tumbler 40 and the rear idler roller 30R, the lugs 50 of the links 28 can hit a lower edge 62 of the end casting 60. Repeated impact of the lugs 50 against the lower edge 62 causes wear to both components, and can eventually damage the end casting 60 to the point where replacement of the end casting 60 or even the frame assembly 32 is required. Damage to the end casting 60 is mitigated in some machines 10 by providing a slide shoe 64 mounted to the lower edge 62 of the end casting 60.
As shown in FIGS. 4 and 5, the lower edge 62 of the end casting 60 is positioned proximate the teeth 56 of the drive tumbler 40 where the links 28 (not shown) roll off the drive tumbler 40 when the tracks 26 are driven in reverse. The slider shoe 64 is affixed to the lower edge 62 by welds or other appropriate connection mechanism. The upper portion of the slider shoe 64 has a shaped surface 66 that corresponds to the shape of the lower edge 62 for attachment thereon. Based on this configuration, the slider shoe 64 is customize for application to the lower edge 62 of the unitary end casting 60, and may not be readily adaptable for other undercarriage frame assembly configurations.
FIG. 6 illustrates one example of an alternative configuration of a rear portion of a frame assembly 70 that is used in undercarriages of alternative machines 10. The frame assembly 70 may be formed by a pair of spaced frame side plates 72I, 72O that extend from the front of the undercarriage to the rear of the undercarriage, and does not include a separate end casting 60 for the rear idler roller 30R and drive tumbler 40 as described above for the frame assembly 32. The left or inner frame side plate 72I is removed in FIG. 6 for purposes of illustrating the support structure connecting the frame side plates 72I, 72O to each other. The rear idler roller 30R and the drive tumbler 40 are also removed, but the positions of the rear idler roller 30R and the drive tumbler 40 will be apparent from a rear idler axle opening 74 and drive tumbler axle opening 76 through the right or outer side plate 72O.
In the illustrated configuration, the spaced frame side plates 72I, 72O are connected by a series of cross supports extending there between. The cross supports include an upper cross support plate 78 connected proximate upper edges 80 of the frame side plates 72I, 72O, a lower cross support plate 82 connected proximate lower edges 84 of the frame side plates 72I, 72O, and an intermediate cross support plate 86 positioned above the rear idler roller axle opening 74. A generally vertical stiffener plate 88 extends from the upper cross support plate 78 to the lower cross support plate 82, and is engaged by a rear edge 90 of the intermediate cross support plate 86 for reinforcement. As shown in FIG. 6, the lower cross support plate 82 is disposed in the gap between the rear idler pulley 30 and the drive tumbler 40. When the drive tumbler 40 drives the tracks 26 forward, the portions of the tracks 26 between the rear idler pulley 30 and the drive tumbler 40 remain taut and spaced from the lower cross support plate 82 so that the lugs 50 of the links 28 do not engage the lower cross support plate 82. In contrast, when the tracks 26 are driven in reverse by the drive tumbler 40, slack can exist in the links 28 as the tracks 26 roll off the drive tumbler 40. As the ground engages the slack portions of the tracks 26, the links 28 bunch up between the drive tumbler 40 and the rear idler roller 30R toward the lower edge 84 of the frame side plates 72I, 72O, and the lugs 50 can engage a rear edge 92 of the lower cross support plate 82. Both the lugs 50 and the lower cross support plate 82 experience wear as a result of the engagement, and in some instances the lower cross support plate 82 can be ripped out of the frame assembly 70 by the lugs 50. In view of this, a need exists for a mechanism for the frame assembly 70 having spaced frame side plates 72I, 72O to prevent buckling of the tracks 26 and engagement of the structures of the frame assembly 70 by the links 28 that can cause wear and damage to the frame assembly 70.